Reverse leakage seal for reciprocating parts



1966 R. J. M CRORY ETAL 3,229,900

REVERSE LEAKAGE SEAL FOR RECIPROCATING PARTS Original Filed April 8.1960 2 Sheets-Sheet 1 ROLLIN J. M CRORY ALBERT K. DAGGETT JOHN B. DAY,JR.

INVENTORS BYfi/dfs ATTORNEYS JOSEPH H. M NlNCH, JR.

Jan. 18, 1966 oc Y ETAL 3,229,900

REVERSE LEAKAGE SEAL FOR RECIPROCATING PARTS Original Filed April 8.1960 2 Sheets-Sheet 2 ROLLIN J. M CRORY ALBERT K. DAGGETT JOHN B. DAY,JR.

IN VE N TORS y%, mm?! ATTORNEYS JOSEPH H. M NlNCH, JR

United States Patent 3,229,900 REVERSE LEAKAGE SEAL FOR REEFRQCAT1NGPARTS Rollin J. McCrory, Worthington, and Joseph H. McNinch, 112,Columbus, Qhio, Albert K. Daggett, Fuilerton, Calif., and John B. Day,.ir., Columbus, @hio, assignors, by mesne assignments, to The BattelleDevelopment Corporation, Columbus, Ghio, a corporation of DelawareOriginal application Apr. 8, 1960, Ser. No. 20,870, now Patent No.3,146,940, dated Sept. 1, 1964. Divided and this application Italy 31,1963, Ser. No. 303,978

8 Claims. (Cl. 230-203} This invention relates to a seal for rapidlyreciprocating parts. More particularly, it relates to a liquid-type sealfor the prevention of fluid flow around the edges of rapid lyreciprocating parts as one moves within the other. This application is adivisional application of our copending application Reverse Leakage Sealfor Recipro cating Parts, Serial No. 20,870, filed April 8, 1960, nowUS. Patent No. 3,146,940, which was a coutinuationdnpart of ourapplication Serial No. 705,334, filed December 6, 1957, now abandoned.

One of the most frequently found uses of seals around reciprocatingparts is in internal-combustion engines and in positive displacementpumps and compressors. Seals frequently used at the peripheral edges ofpistons where contact is made with a cylinder wall are steel pistonrings, packings of felt or rope, and O-rings. These are, of course,satisfactory in many and most applications. However, in thoseapplications where the pressure differential between one side of thepiston and the other is high and the rate of reciprocation is high, theproblem of sealing is very difficult. Also, in certain installationswhere the operative fluid on the high pressure side of the piston shouldnot be lost because of the expense involved in maintenance andreplacement, the problem of providing an adequate seal is mostimportant. When these conditions are combined, i.e., in installationswhere the pressure differential is high, the rate of reciprocation ishigh, and the prevention of loss is very important, the provision of anadequate seal is most critical and may be the difference between successand failure of a unit for a particular application.

One such instance is found in the problem of sealing a refrigerant-gascompressor that is operatively connected to, and may be integral with, afree-piston internal-com bustion engine. Free piston internal-combustionengines may operate at a high cyclic rate up to 4000 cyles per minute.When constructed in conjunction with a gas compressor, a free-pistonengine imparts the same rate to the compressor piston. When afree-piston-engine-actuated refrigerant-gas compressor, hereinafterreferred to as a free-piston engine compressor, is used in therefrigeration system of an air-conditioning unit or other similarrefrigeration system, it is important that the refrigerant gas loss beheld to a very small figure so that the system need not be chargedoftener than once each year and preferably not oftener than every fiveyears.

It has been found that ordinary seals such as piston rings, O-rings, andpackings are not suitable as seals for the compressor piston in afree-piston engine compressor, because of either leakage, prematurefailure, or excessive friction.

This invention comprises sealing apparatus and a sealing method for thepiston of a free-piston engine compressor, or other rapidlyreciprocating parts, that provide for withstanding the rigors of thistype of service. In one embodiment of this invention, the piston of thecompressor is provided with a recess at its outer peripheral surface inwhich is disposed a sealing liquid in contact with the cylinder wall.Means is provided to control the pressure of the sealing liquid so thatliquid flow takes place toward the compressor chamber. The flowingliquid therefore blocks the passage of gas from the compressor chamber.Means is provided to collect and separate the sealing liquid from thegas and return the sealing liquid at proper pressure to the enclosureformed by the recess in the piston and the cylinder wall.

It is therefore the broad purpose of this invention to provide a sealwhich will satisfactorily prevent the passage of fluid around theposition of contact between rapidly reciprocating parts. It is anotherpurpose to establish a method of liquid sealant control and movement ina sealing system which will insure that the liquid sealant will flow inthe proper direction to block the passage of compressor fluid. It is afurther purpose to also provide a method of sealing wherein the pressurein the fluid is controlled so that the pressure in the liquid sealant,when at the surface of contact between the reciprocating parts, is at apressure higher than the pressure in the compressor chamber asubstantially uniform increment throughout the cycle of the compressor.

It is another purpose of this invention to provide apparatus which willcontrol the pressure in the liquid sealant of a refrigerant-gascompressor to an amount that will provide minimum loss of refrigerantgas through the sealing liquid.

It is another purpose of this invention to provide apparatus which willcontrol the pressure of the refrigerant gas of a refrigerant gascompressor above the compressor chamber to an amount below the pressureof the liquid sealant thereby providing a flow of sealing liquid in adirection toward the compressor chamber to provide a minimum loss ofrefrigerant gas from the compressor system.

Features of this invention are: the way in which a seal is providedwithout excessive frictional resistance to motion between reciprocatingparts; the way in which the seal is constantly replaced and thereforethere is no appreciable wear on the seal and no lost time in replacingworn components; the way in which the problem of fluid loss through theliquid sealant is overcome by the control of the sealing liquidpressure; the way in which the problem of fluid loss through the sealingliquid is overcome by the control of the fluid pressure adjacent to thesealing gland; and the way in which a satisfactory seal is provided in afree-piston engine compressor making such a power source convenientlyusable in refrigeration systems.

To these and other ends, this invention comprises apparatus for and amethod of sealing around reciprocating parts, the preferred form ofwhich is disclosed in the following description and attached drawing.Although the apparatus, structure, and method decribed and shown indetail refer with particularity to a free-piston engine refrigerant-gascompressor, it is apparent that this invention should not be limitedthereto. Many of the significant details of this invention apply withequal qualification to the sealing of reciprocating parts in general.The invention may be used for other purposes, where its features areadvantageous.

In the drawings:

FIG. 1 is a sectional elevational view of a compressor havingconstructed therein one form of the sealing apparatus of this invention,which employs the method of this invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a schematic view of another form of a portion of the sealingapparatus of this invention, which employs the method of this invention;

FIG. 4 is a schematic view of another form of the sealing apparatus ofthis invention, which employes the method of this invention.

Referring to FIG. 1, an cylinder 12 forms the outer housing or framemember of a compressor, designated generally as 11. The compressor 11may be formed integrally as a part of the frame of a compressoractuating device, such as a free-piston engine designated generally as13. The details of construction of a free-piston engine may vary and ingeneral are well known.

The free-piston engine 13 comprises a combustion cylinder 14 and alarger diameter control cylinder 15, having a piston 16 mounted theerinfor reciprocable motion. The piston 16 comprises a major diameterportion 17 adapted to reciprocate in the control cylinder 15, and aminor diameter portion 18 constructed to reciprocate in the combustioncylinder 14. The combustion cylinder 14 forms a combustion chamber 19 inconjunction with the minor diameter portion 18. Major diameter portion17 partitions control cylinder into a pump chamber 23 at one side and arebound control chamber 2!} at the opposite side. Ignition means 21 suchas a spark plug may be provided in the head end of the combustionchamber 19.

Auxiliary well-known equipment such as a source of electrical potentialfor the spark plug 21 and a means of injecting fuel into the combustionchamber 19 are provided, together with proper porting and otherconstruction features.

At the one side of the larger diameter portions 17 of the piston 16, aconnecting rod 22 is either integrally formed with the piston 16 orfastened rigidly thereto. The connecting rod 22 extends into thecompressor cylinder 12, and in the embodiment of the invention shown inFIG. 1, is formed into a first compressor piston 25. Piston 25 isconstructed to reciprocate by sliding fit along an inner wall 26 ofcylinder 12. Sealing members 70, which may be conventional piston rings,are provided in grooves on the outer peripheral surface of the firstcompressor piston 25 to prevent the flow of liquid upward into a chamber24 above. A second compressor piston 27 having a first major diameterportion 28, an intermediate recessed diameter portion 29, and a minordiameter guide portion 30, is constructed to reciprocate in cylinder 12by sliding telescoping fit at an adjacent spaced position below thefirst compressor piston 25. Minor guide diameter portion 30 is receivedin a bore 31 centrally positioned in the lower face of first compressorpiston 25. The outer surface of the guide portion 30 is provided with aseal 32, which may be an O-ring in a groove. A slot 33 is transverselylocated adjacent the upper end of the minor diameter portion 30. Slot 33receives a transversely positioned pin 34 which is disposed in areceptive pin bore 35 through opposite sides of piston 25.

The above-described construction, consisting of the first compressorpiston 25 and second compressor piston 27, comprise a partition unitwhose major diameter has a surface of contact along the inner wall 26 ofcylinder 12. The surface of contact has a cavity or an enclosure formedby the wall 26 of cylinder 12, the surfaces of piston 27 including therecess portion 29 and the minor diameter portion 30, the intermediatestep portion 41 which is between, and the lower surfaces 42 of thepiston 25.

Piston 27 may be hollow, as shown in FIG. 1, if it is desirable tolessen its weight.

Cylinder 12 is constructed with a plurality of apertures, including asuction inlet 43, having an inwardly opening check valve 44; a dischargeoutlet 45 having an outwardly opening check valve 46; and a sealantinlet 47 having an inwardly opening check valve 48. Inlet 47 is incommunication with the enclosure 40 at all time. A sealant liquid 52,which may be oil, is provided in the enclosure 40.

At one end 49, piston 27 forms a compressor chamber 50 in conjunctionwith the walls 26 and a closure end 51 of cylinder 12.

The free-piston engine 13 operates through the combustion of fuel in thechamber 19 forcing piston 16 downward in the power stroke. The downwardstroke compresses refrigerant gas in the compressor chamber 50. At theend of the power stroke, piston 16 is returned to headend position byenergy in the refrigerant gas. Air trapped in central chamber 20 andpump chamber 23 may be vented or utilized to control the stroking ofengine 13.

When the minor diameter portion 18 uncovers the exhaust ports on thedownward stroke, the pressure in combustion chamber 19 is immediatelyreduced. While the pressure in chamber 19 decreases, the pressure incompressor chamber 50 remains high as the piston continues downward bymomentum. When the downward kinetic energy is consumed the pistonreverses and starts up, driven by the gas in compressor chamber 50 atdischarge pressure. The pressure in chamber 50 immediately decreases,and as soon as the pressure in compressor chamber 50 decreasessuificiently to create a negative pressure differential across valve 44,valve 44 opens. The opening of valve 44, allows chamber 50 to fill withgas from the suction inlet 43. Substantially at the same time dischargeoutlet valve 45 closes because the pressure on the discharge side ishigher than the side toward chamber 50. The pressure of the gas admittedthrough valve 44 is high enough to force second compressor piston 27upward. The upward force is transferred through the liquid in enclosure40, the first compressor piston 25, and the connecting rod 22. Thus, bymeans of the suction pressure of the compressor gas, the piston 16 isreturned to head-end position on the intake stroke of the engine 13,completing the combustion cycle.

Upon the commencement of the downward stroke of first compressor piston25, valve 44 closes. During the downward stroke the passage of liquidupward around minor diameter portion 30 is prevented by sealing member32. Accumulation of pressure in bore 31 above the upper end of portion30 is prevented by means of a vent 53. When the pressure in chamber 50becomes greater than the pressure in the discharge line 55, valve 46opens and gas in discharged from outlet 45 into discharge line 55.

Since the area of piston 27 that is in contact with the sealant liquid52, normal to the axis of the piston, is less than the area of thepiston 27 in contact with the gas in chamber 50, normal to the axis ofthe piston 27, the pressure of the sealant liquid 52 .is higher than thepressure of the gas in chamber 50. Therefore, any leakage between thesliding contact surface of the piston 27 and the wall 26 is oil leakagetoward the compression chamber 50. Since any space, no matter how smallor large, between the piston 27 and the wall 26 is occupied by oilflowing toward the compressor chamber, the gas in compressor chamber 50is effectively prevented from leaking and is sealed from passage aroundthe reciprocating components of the apparatus.

Because of suction pressure remaining in compression chamber 50 when theengine is shut oh, the piston 16 always comes to rest at head-endposition, opposite to that shown in FIG. 1. In order to provide a staticseal for the compressor unit during periods when the apparatus is not inoperation, a static seal 56, which may be an O-ring, is provided in agroove 57 at the upper end of cylinder 12. When the engine stops athead-end positions, the upper face of piston 25 rests against the seal56 and prevents the escape of gas until the engine is started and theliquid seal is in operation.

Referring further to FIG. 1, discharge line 55 is connected into the topof an enclosed separator reservoir 58. A compressed gas dischargeline 59is connected to the top of separator 58. At a position near the bottom aconduit 60 is connected from the separator 58 into a stripper.

61. t The stripper 61 is an enclosed vessel having an outlet conduit 62at the top in communication with a check valve 63. Check valve 63 is incommunication with, and opens toward, the inlet suction line 64 to theinlet suction valve 43 of compressor 11.

At the discharge end of conduit 60 in stripper 61, is a float valve 65of conventional construction which opens responsively to the liquidlevel in stripper 61. A source of heat, representatively shown as aflame 67, is provided beneath the stripper 61. From a position near thebottom and below the liquid level, a conduit 68 connects stripper 61 tothe sealant liquid inlet 47 on the cylinder 12.

In the operation of the apparatus and method of this invention thesealant liquid passes into the compressor chamber 50. In order that thissealant liquid shall not be Wasted the discharge line 55 is connected tothe sepa-rator 58 wherein the large particles and liquid droplets ofsealant liquid 52 collect by gravity at the bottom. The compressed gasis then discharged through the line 59 for whatever use it has beencompressed.

In an air compressor this may be the operation of an operating device inwhich case the sealant liquid, which would probably be oil, is used toadvantage to lubricate the operating device. In other instances, thecompressor gas may be a refrigerant gas such as Freon l2, and smallparticles may be carried into the discharge and refrigerator systemwithout harm, being returned in the suction line 64. Therefore, theabsorption of the liquid sealant in the compressor gas system is notusually detrimental to the operation of the apparatus and method.

On the other hand, any means by which the refrigerant gas may be carriedin the return of the sealant liquid to the enclosure 40 is verydetrimental to the operation of the system. The main detriment is theloss of gas, which in the case of a refrigerating system, may not betolerated in most instances.

In many refrigeration systems the discharge pressure is as high as 150to 200 p.s.i. absolute; the suction pressure is about 50 p.s.i.absolute; and the temperature of the refrigerant gas may reach as highas 200 F. during the compression stroke. In the normal reciprocation ofthe piston 27, a film of liquid sealant is deposited on the walls 26 ofthe chamber 50, and it has been found that a liquid sealant such as oilwill dissolve a refrigerant gas, such as Freon 12, at the temperatureand pressure existing in the compressor chamber 50. This dissolved gasis carried into the reservoir in the separator 58. Sealant liquid ispumped through the conduit 60 by reason of a high pressure in theseparator 58 and discharges into the stripper 61 until the float valve65 is actuated by the level of the sealant liquid 52 by raising thefloat 66. The application of heat from the flame source 67 to the liquid52 in the stripper 61 evaporates the compressor gas from the liquid atthe surface into the accumulator chamber above. The gas then passesthrough the outlet 62 to the pressure differential valve 63. Pressurediiferential valve 63 is adjusted to open when the gas pressure in thestripper 61 becomes more than about pounds greater than the suctionpressure to the compressor.

In a refrigeration system as previously described having a suctionpressure of about 50 pounds the pressure differential valve 63 isadjusted to open at 60 p.s.i. abso lute. Therefore, the pressure on theliquid sealant in the stripper 61 is maintained at a pressure of about60 pounds and the dissolved gas may be stripped until only a negligibleamount of gas remains in the liquid at this low pressure. The liquidsealant is carried through the conduit 68 to the liquid sealant inlet 47and is admitted to the enclosure 40 upon the opening of the check Valve48 whenever the pressure in the enclosure 40 is less than the pressurein the stripper 61. The check valve 48 will therefore open wheneverleakage past piston 27 lowers the pressure in enclosure 40 sufficiently.

It has been found in the operation of the compressor, if the lowpressure stripper 61 is not provided, the oil is carried back to theenclosure 40 carrying dissolved gas with it. A film of oil is depositedon the upper wall 26 of the cylinder 12 by reason of the movement of thepiston 25 and the enclosure 40 to its uppermost position. The dissolvedgas will be evaporated and lost at the lower pressure condition whichexists above the piston 25, when the piston 25 is at its lowermostposition. In the refrigeration apparatus of the example the low pressurestripper 61 evaporates the dissolved refrigerant gas, carrying it backto the refrigeration system and preventing its loss from the oil inchamber 24 above enclosure 40.

By means of the apparatus disclosed, and by means of the method ofoperating the seal so that pressure condi tions in the sealant liquidcause flow toward the compressor chamber, in conjunction with the lowpressure stripping process step, it has been found that the compressorsystem may be operated over prolonged periods of time with negligiblelosses of gas from the system.

Although the apparatus and the method disclosed and shown in FIGS. 1 and2 are particularly advantageous in their application to the problem ofsealing a rapidly reciprocating refrigerant gas compressor, certain ofthe features of the invention may be utilized in different forms ofapparatus and when using different sealing liquids and compressorgasses.

Referring to FIG. 3, a reciprocating piston compressor is schematicallyshown of a different form although employing the method of theinvention. A gas compressor designated generally as comprises acylindrical frame 111 and a piston 112 constructed to reciprocatetherein by sliding fit. The frame 111 may form a part of a free-pistonengine or other operating device. Piston 112 may be connected to a freepiston or crank arm by means of the up standing connecting rod portion113. Piston 112 forms a compressor chamber 114 in conjunction withcylinder 111 and the closure means 115 at one end. An inwardly opening,inlet check valve 116 of conventional construction and an outwardlyopening discharge check valve 117, also of conventional construction,are provided in communication with the chamber 1114.

Cylinder 111 is provided with a minor diameter portion near thecompressor end changing to a major diameter portion near the oppositeend. Piston 112 is provided with mating sliding contact portions 120 and121 separated by a recessed portion 122. Recess portion 122 forms anenclosure 123 in conjunction with cylinder 111. At one side of cylinder111, is provided a conduit 124 in communication with a surge tank 125. Asealant liquid 126 is provided in the enclosure 123, conduit 124, andsurge tank 125. A sealant supply line 127 connects with the surge tank125 through an inwardly opening check valve 128.

As in the apparatus of FIGS. 1 and 2, the compressor 110 is connected toother apparatus requiring the compressed gas and the connection may bemade through a separator. The separator may be connected through astripper to the sealant liquid supply line 127. However, the successfuloperation of the method and apparatus only requires that the supply line127 be connected to a source of sealant liquid having a pressure greaterthan the pressure in the surge tank and enclosure 123 at some timeduring reciprocation of the piston 112.

In the operation of the apparatus, shown in FIG. 3 as the pistondescends on the compression stroke, the volume of the enclosure 123 isdecreased by reason of the advancing proportion of the major portion ofthe cylinder 111 in enclosure 123. The decreases in volume of theenclosure 123 forces the liquid sealant 126 out through the conduit 124into the surge tank 125. The increase in the amount of sealant liquid inthe surge tank 125 decreases the accumulator volume above the liquid 126in surge tank 125 and, therefore, increases the pressure in theaccumulator portion. The increase in the pressure in the surge tank 125causes the pressure in the liquid 126 to increase progressively with theadvance in downward stroke of piston 112. The volume and proportion ofthe Various parts are arranged such that the pressure in the enclosure123 increases proportionately with the increase in compressor chamber114 'be in the direction of the chamber 114 and will seal the compressorchamber against loss of compressor gas around the sides of the piston112.

On the upstroke of the piston 112, when the pressure in enclosure 123becomes lower than the pressure in the stripper, check valve 128 opensand admits sealant liquid to the surge tank 125 and enclosure 123 asnecessary for replacement. Sealant liquid which flows past the minordiameter 120 of piston 112 into compressor chamber 114 flows out throughthe discharge outlet and may be trapped in a separator as necessary in amanner similar to that shown for the seal apparatus of FIG. 1.

FIG. 4, discloses a piston-cylinder apparatus which employs certainfeatures of the method of this invention. In FIG. 4, a compressordesignated generally as 150 comprises a cylinder 151 and a piston 152.Cylinder 151 may be connected to or formed as a part of the frame of adriving device such as a free-piston engine,

not shown. Piston 152 is provided with a connecting rod portion 153(partially shown) at one end. Connecting rod portion 153 is connected toan actuating mechanism of the driving device.

Cylinder 151 is provided with an outwardly opening discharge valve 154and an inwardly opening suction valve 155 each of which may be connectedin apparatus of the type shown in FIG. 1 or in apparatus of the typeshown in FIG. 4. An inlet 156 for a sealant liquid 161 is provided inone side of cylinder 151.

Piston 152 is provided with annular extremity portions which reciprocatein piston 151 by sliding fit. A

central recessed portion 159 provides, in conjunction with cylinder 151,an enclosure 160, which is filled with the sealant liquid 161.

In those installations where the loss of compressor gas by beingdissolved in the liquid sealant, is not a critical factor, such as in anair compressor, the compressor discharge outlet 154 may be connected toa separator 162 which is in communication by means of a line 163 to thesealant liquid inlet 156. A check valve 170 is provided in the line 163and is positioned to open toward inlet 156. Separator 162 is alsoprovided with a compressor gas discharge line 164. Flow is in thedirection indicated by the arrows in FIG. 4. Heat from a source 165 maybe applied beneath separator 162 to facilitate the separation ofcompressor gas and liquid sealant.

The apparatus shown in FIG. 4 applies the sealing method of thisinvention in the following manner. On the down stroke of the piston 152,gas is compressed in the chamber 166 and is forced into the separator162. The pressure of the liquid sealant 161 which is present in thereservoir of the separator 162, in the line 163, and the enclosure 160is therefore maintained at the compressor discharge pressure duringoperation. At the beginning of the down stroke piston 152, the pressurein chamher 166 is at the suction pressure of the gas which has beenadmitted through suction inlet valve 155 on the up stroke. As the piston152 progresses downward the pressure increases to compressor dischargepresure. During that period of the stroke when the pressure incompressor chamber 166 is equal to compressor discharge pressure and tothe pressure of the liquid sealant 161, the liquid sealant is not forcedto flow toward chamber 166. However, during the upward stroke of thepiston the pressure of the sealant liquid 161 is higher than thepressure of the compressor gas and flow will positively be inducedtoward the chamber 166. Flow cannot take place in the opposite directionbecause of check valve 170 in line 163. Because of the width of thelower contact flange of piston 152, any gas which is wiped towardenclosure during the period when the pressure in chamber 166 is equal tothe pressure in enclosure 160, will be wiped back and forced towardchamber 166 during other periods in the stroke.

Factors which have a bearing on producing the proper proportion toprovide the required sealant flow conditlons are: the ratio of suctionpressure to dischargepressure in the compressor, the character of thesliding fit between the piston and the cylinder, and the characteristicsof the compressor gas and the sealant liquid.

Each of the apparatuses shown utilizes the basic method of thisinvention which comprises the following steps: confining a sealingliquid at the surface of contact between rapidly reciprocating parts,regulating the pressure of the sealing liquid to a value higher than thepressure of a fluid at one side of one of the parts for a sutficientlylong period to provide greater sealing liquid flow towards said fluidthan away from said fluid, collecting the sealing liquid in the fluid,separating the sealing liquid from the fluid, and returning the sealingliquid to the contact position.

In the forms of apparatus shown in FIGS. 1, 2 and 3, the sealing liquidpressure'is maintained higher than the fluid pressure at all times.Thus, the pressure of the sealing liquid is maintained at a valuehigherthan the pressure of the fluid for a time sufficiently long to provideflow towardthe fluid. In the form of apparatus shown in FIG. 4 thepressure of the sealing liquid is not maintained higher than the fluidpressure at all time, but is maintained at a higher pressuresufliciently long to provide sealing liquid flow towards said fluidduring a portion of the stroke.

It will be understood, of course, that, while the forms of the inventionherein shown and described constitute the preferred embodiments of theinvention, it is not intended herein to illustrate all the possibleequivalent forms or ramifications of the invention. It will also beunderstood that the words used are words of. descript1on, rather than oflimitation, and various changes, such as changes in shape, relativesize, and arrangement of parts may be substituted without departing fromthe spirit and scope of the invention herein disclosed.

What is claimed is:

1. A seal construction for rapidly reciprocating positive displacementgas compressors having a cylinderand a piston unitary reciprocabletherein, and having closure means for one end of said cylinder forming acompressor chamber in conjunction with said cylinder and the contiguousend of said piston; comprising: an annular pecompressor chamber; andcommunication means between said stripper and said inlet in saidcylinder wall.

2. -A sealing construction for cylinder and piston units for theprevention of fluid flow around said piston at the surface of contactbetween the piston and the cylinder Wall, comprising: a cylinder havingan inlet through the wall thereof; a piston unit constructed toreciprocate in said cylinder by a sliding fit, having an annular contractible recess at the outerperipheral edge thereof and comprisingcontractible connected elements; said recess in communication with saidinlet within the length of the stroke of said piston unit, and saidrecess forming an enclosure in conjunction with said cylinder wall; asealing liquid in said enclosure, check valve means in communicationwith said inlet operative to close when the axial forces at the ends ofsaid unit contract said enclosure, to raising the pressure of saidsealing liquid to a value greater than the fluid pressure at the surfaceof contact between the piston unit and the cylinder wall upon thereciprocation of said piston unit in one direction in said cylinder.

3. A seal construction for rapidly reciprocating positive displacementgas compressors having a cylinder and a piston unit reciprocal therein,and closure means for one end of said cylinder forming a compressorchamber in conjunction with said cylinder and the contiguous end of saidpiston unit, wherein: said piston unit comprises first and secondpistons; said second piston is reciprocable in said cylinder and formed.a recessed portion of smaller diameter than said sliding reciprocableportion;

said second piston is contractibly connected tos'aid first.

piston; said recessed portion forms an enclosure in conjunction withsaid piston connection and said cylinder wall, and the effective area ofcontact of said second piston with said enclosure is less than theeffective area of said contiguous end of said piston unit; and whereinthere is included; an inlet in the wall of said cylinder incommunication with said enclosure at all positions during said pistonreciprocation; separator means in communication with the discharge ofsaid compressor chamber; a check valve in said inlet operable to closewhen the pressure in said enclosure exceeds the pressure in saidseparator chamber; stripper means in communication with said separatormeans through a valve operated responsively to the liquid level in saidstripper means; pressureresponsive gas discharge means in communicationwith said stripper; and communication means between said stripper andsaid inlet to said cylinder wall.

4. A seal for the prevention of fluid passage past reciprocating partswhich operate between opposite chambers containing fluids, comprising: acylinder having an inlet in the side thereof and having a closure at oneend to form a chamber and having oppositely actuated check valve meanstherein to provide fluid pumping action on reciprocation of said piston;a first piston reciprocable in said cylinder by sliding fit, and havingguide means therein; a stepped second piston axially spaced andreciprocable in said cylinder in sliding fit, having a first portion ofreduced diameter and an attachment means loosely connecting said firstpiston and said second piston through said guide means; said firstportion of reduced diameter forming an enclosure in conjunction withsaid first piston; a sealing liquid in said enclosure; and means forsupplying a liquid sealant to said enclosure at a pressure greater thanthe pressure in said chambers during reciprocation of said piston in onedirection.

5. A seal according to claim 4 wherein said guide means and looselyconnecting means comprises a third piston reciprocable in a cylinder inone of said other pistons, and a slot and pin toggle.

6. A seal for the prevention of fluid passage around reciprocating partswhich operate between opposite chambers containing fluids, for theprevention of fluid flow from one chamber to the other, comprising: aframe member, having a larger portion and a smaller portion; a partitionmember, having a larger portion constructed to reciprocate in the largerportion of said frame member by a sliding fit, and having a smallerportion constructed to reciprocate in said smaller portion of said framemember by a sliding fit, said partition member having a recess portioncommunicating with :both the larger and the smaller portions of saidframe member, forming an enclosure in conjunction with said framemember, an inlet in the wall of said frame member in communication withsaid enclosure at all positions in the stroke of reciprocation of saidpartition member; a pressure accumulative reservoir in communicationwith said inlet; and a liquid in said reservoir and said enclosure at apressure greater than the pressure in at least one of said chambersduring the stroke of reciprocation of said partition member.

7. A seal for the prevention of fluid passage around telescopingreciprocating parts which operate between opposite chambers containingfluids for the prevention of fluid flow from one chamber to the other,comprising: a frame member having a larger portion and a smallerportion; a partition member, having a larger portion constructed toreciprocate in the larger portion of said one frame member by a slidingfit, and having a smaller portion constructed to reciprocate in thesmaller portion of said frame by a sliding fit, said partition memberhaving a recessed portion communicating With both the larger and smallerportions of said frame member, forming an enclosure in conjunction withsaid frame member;

an inlet in the wall of said frame member in communicagreater than thepressure in at least one of said cham bers during the reciprocation ofsaid partition member; separator means in communicaton with thedischarge of said one of said chambers; stripper means in communicationwith said separator means through a valve operated responsively to theliquid level in said stripper means; pressure responsive fluid dischargemeans in communication with said stripper; and communication meansbetween said stripper and said inlet.

8. A seal construction for rapidly reciprocating positive displacementgas compressor-s having a cylinder and a piston reciprocable therein,and closure means for one end of said cylinder forming a compressorchamber in conjunction with said cylinder and the contiguous end of saidpiston, comprising: a cylinder having a larger diameter portion and asmaller diameter portion in longitudinally spaced relation; said pistonhaving a larger diameter portion constructed to reciprocate in thelarger diameter portion of said cylinder by a sliding fit, and having asmaller diameter portion constructed to reciprocate in the smallerdiameter portion of said cylinder by a sliding fit, said piston having arecessed portion communicating with both the larger and the smallerportions of the cylinder, forming an enclosure in conjunction with thecylinder; an inlet in the wall of the cylinder in communication withsaid enclosure at all positions in the stroke of recirpocating of saidpiston; a check valve in lative reservoir in communication With saidinlet; a liquid in said reservoir and said enclosure at a pressuregreater than the pressure in said compressor chamber during the strokeof reciprocation of said piston; a check valve in said inlet operable toclose when the pressure in said enclosure exceeds the pressure in saidcompressor chamber; separator means in communication with the dischargeof said compressor chamber; stripper means in communication with saidseparator means through a valve operated responsively to the liquidlevel in said stripper means; pressure responsive gas discharge means incommunication with said stripper; and communication means between saidstripper and said inlet to said cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,260,100 3/1918Udell 230203 2,330,781 9/ 1943 Langmyhr et a1. l03204 FOREIGN PATENTS73,718 11/ 1916 Switzerland.

DONLEY J. STOCKING, Primary Examiner.

ROBERT M. WALKER, LAURENCE V. EFNER,

Examiners.

1. A SEAL CONSTRUCTION FOR RAPIDLY RECIPROCATING POSITIVE DISPLACEMENTGAS COMPRESSORS HAVING A CYLINDER AND A PISTON UNITARY RECIPROCABLETHEREIN, AND HAVING CLOSURE MEANS FOR ONE END OF SAID CYLINDER FORMING ACOMPRESSOR CHAMBER IN CONJUNCTION WITH SAID CYLINDER AND THE CONTIGUOUSEND OF SAID PISTON; COMPRISING: AN ANNULAR PERIPHERAL RECESS IN SAIDPISTON FORMING AN ENCLOSURE IN CONJUNCTION WITH SAID CYLINDER; SAIDENCLOSURE ADAPTED TO CONTAIN A SEALING LIQUID; AN INLET IN THE WALL OFSAID CYLINDER IN COMMUNICATION WITH SAID ENCLOSURE AT ALL POSITIONSDURING SAID PISTON RECIPROCATION; SEPARATOR MEANS IN COMMUNICATION WITHTHE DISCHARGE OF SAID COMPRESSOR CHAMBER; STRIPPER MEANS INCOMMUNICATION WITH SAID SEPARATOR MEANS THROUGH A VALVE OPERATEDRESPONSIVELY TO THE LIQUID LEVEL IN SAID STRIPPER MEANS;PRESURE-RESPONSIVE DISCHARGE